The objective of this research is to examine the genetic and physiologic regulation of pili in E. coli, K. pneumoniae and S. typhimurium. Genetic analyses will be performed using DNA recombinational techniques including gene cloning, construction of hybrid plasmids and DNA base sequencing. These techniques will be used to determine the parameters affecting the control and expression of pili by enterobacteria. A knowledge of such regulatory mechanisms, at the molecular level, should facilitate a better understanding of microbial adherence phenomena. Genes coding for the type-1 pili of K. pneumoniae and S. typhimurium will be cloned using the Lambda in vitro packaging system and suitable cloning vehicles. An analysis of both structural and regulatory genes is proposed so that comparisons of the control and regulation of these adhesions may be accomplished. Similar studies will be performed using the genetic elements coding for MR pili of E. coli. Parameters affecting control of regulatory genes will be analyzed by the use of lac-fusion plasmids. The elucidation of the regulation of pili may lead to a further insight into methods by which bacteria control phenotypic expression of surface antigens.